The present invention relates to the making of threads in cylindrical portions of workpieces, and more particularly to improvements in a method of and in a machine for grinding threads in cylindrical portions of workpieces.
It is already known to grind threads into the peripheral surface of a workpiece which is held between a headstock and a tailstock and is movable therewith axially with reference to a grinding tool. It is further known to provide a grinding machine wherein the workpiece is mounted in the just described manner with a grinding wheel holder which is angularly movable in the machine. A drawback of conventional thread grinding machines is that the grinding of workpieces invariably involves several operations one of which includes grinding the workpiece for the purpose of ensuring that the diameter of the ultimate product will match the desired value and the other of which includes forming the thread in the peripheral surface of the workpiece. Thus, each workpiece is caused to move along the grinding tool or tools for a first time in order to complete one of the just enumerated operations, and a second pass is required to perform the other operation. This is a time-consuming procedure. Moreover, the versatility of heretofore known thread grinding machines is rather low, i.e., though a conventional machine is capable of grinding threads on several types of workpieces, the shape of threads and/or the dimensions of workpieces which can be treated in conventional machines is limited. Still further, repeated transport of one and the same workpiece past a grinding tool invariably brings about at least some deviations from the desired optimum dimensions and configuration of the ultimate products.